The present invention relates to an apparatus and method for detecting the thickness of record media in a feed path, and more particularly relates to such an apparatus and method in which record media thickness is measured during passage of the record media along a feed path between record medium drive means (which may be formed by drive belts or rolls) and cooperating roll means.
The apparatus which is the subject of the present invention may be employed in a variety of applications in which it is desired to measure the thickness of record media as said media traverse a feed path. One such application is in a document processing module which is employed in automated teller machines (ATMs) widely used by financial institutions such as banks. The module is capable of accepting a document from a bank customer and processing it according to its type. If a single sheet document such as a check or giro form is input by the customer, it is passed to an image processing unit along one feed path. If an envelope (which may contain currency or cheques) is input by the customer, it is passed to a secure bin along another feed path.
The correct feed path is selected by the customer by keying in to the ATM customer keyboard the correct information about the type of document. If, for example, the customer incorrectly inserts an envelope when performing a cheque transaction, the envelope would be passed to the image processing unit. This envelope could be of a greater thickness than that which the image processing unit can handle, and the envelope might therefore become jammed in the feed path, or could damage the image processing unit.
The thickness sensing mechanism is therefore required to insure that documents or other record media of greater than a given thickness are not passed into the image processing unit. The main requirements for such a thickness indicating mechanism are reliability and low cost. Displacement transducers such as an LVDT (linear variable differential transformer) could be used, and would provide a reliable mechanism, but are expensive to implement.